Driving circuit for a microwave oven

Abstract

A microwave oven driving circuit for stably driving a microwave oven wherein a certain output of a magnetron can be generated by controlling a microcomputer. First and second comparing portions control a voltage supplied from a power supply portion and an output of the magnetron to increase in stages so as to obtain a normal output of the magnetron. Also, the output of the magnetron is gradually decreased without being too abrupt even if the output of the generating portion must be decreased as cooking is completed, thereby improving durability and cooking efficiency of the microwave oven.

What is claimed is: 
     
       1. A driving circuit comprising: a power supply portion including a transformer having a primary coil and a secondary coil for outputting power;   a generating portion, electrically connected to receive power output from said secondary coil of said transformer, for generating an ultrahigh frequency;   a first comparing portion, electrically connected to said primary coil of said transformer, for comparing a voltage proportional to a current in said primary coil of said transformer to a first threshold voltage and for generating an output to control said output of said secondary coil of said transformer;   a second comparing portion, electrically connected to an output of said generating portion, for comparing said output of said generating portion to a second threshold value, wherein said first threshold voltage includes an output of said second comparing portion, which is an input of said first comparing portion; and   a switching portion, electrically connected to said second comparing portion, capable of selectively setting said first threshold voltage to control said output of said secondary coil of said transformer, wherein said switching portion increases the output of said secondary coil of said transformer at an initial operating stage of said generating portion, and decreases the output of said secondary coil of said transformer in accordance with a program stored in said switching portion.   
     
     
       2. A driving circuit according to claim 1, wherein said switching portion includes a microprocessor. 
     
     
       3. A driving circuit according to claim 2, further comprising key-input portion for inputting data to control said microprocessor. 
     
     
       4. A driving circuit according to claim 1, wherein said generating portion includes a magnetron. 
     
     
       5. A driving circuit according to claim 1, wherein said power supply portion includes a full rectifier. 
     
     
       6. A driving circuit according to claim 1, wherein said switching portion comprises a group of transistors and a plurality of resistors connected to respective transistors. 
     
     
       7. A driving circuit according to claim 1, wherein said first comparing portion compares an inverted voltage proportional to a current in said primary coil of said transformer and the output voltage of said second comparing portion.